Add USE_RTTI and default behavior to CMakeLists

Summary:
Proposed fix for #3701
Closes https://github.com/facebook/rocksdb/pull/3801

Differential Revision: D7868264

Pulled By: gfosco

fbshipit-source-id: 013963ed3d172c8dc2abd1dd5982580082ca5d2d

CMakeLists.txt

@@ -16,7 +16,7 @@
 #    See thirdparty.inc for more information.
 #        sample command: cmake -G "Visual Studio 15 Win64" -DWITH_GFLAGS=1 -DWITH_SNAPPY=1 -DWITH_JEMALLOC=1 -DWITH_JNI=1 ..
 # 4. Then build the project in debug mode (you may want to add /m[:<N>] flag to run msbuild in <N> parallel threads
-#                                          or simply /m ot use all avail cores)
+#                                          or simply /m to use all avail cores)
 #        msbuild rocksdb.sln
 #
 #        rocksdb.sln build features exclusions of test only code in Release. If you build ALL_BUILD then everything
@@ -309,6 +309,20 @@ else()
    set(OPTIMIZE_DEBUG ${OPTIMIZE_DEBUG_DEFAULT})
 endif()
 
+if(DEFINED USE_RTTI AND USE_RTTI EQUAL 1)
+  message(STATUS "Enabling RTTI")
+  set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DROCKSDB_USE_RTTI")
+  set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -DROCKSDB_USE_RTTI")
+elseif(DEFINED USE_RTTI AND USE_RTTI EQUAL 0)
+  message(STATUS "Disabling RTTI")
+  set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -fno-rtti")
+  set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -fno-rtti")
+else()
+  message(STATUS "Enabling RTTI in Debug builds only (default)")
+  set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DROCKSDB_USE_RTTI")
+  set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -fno-rtti")
+endif()
+
 if(MSVC)
   if((${OPTIMIZE_DEBUG} EQUAL 1))
     message(STATUS "Debug optimization is enabled")